TRANSVERSE SECTIONS. 



85 



2. The epidermis lies immediately below the cuticle. It 

 consists of a single layer of columnar cells, set side 

 by side at right angles to the surface, with nuclei 

 near their bases. Many of these cells have the 

 character of ' goblet cells,' being distended by a 

 granular secretion formed within them ; other cells 

 lying between these are extremely slender. In the 



Fig. 27. Lumbrieus. A diagrammatic transverse section through the 

 middle of the body. On the left side of the figure a nephridium is 

 shown, and on the right side the setse. The septa are not shown, 

 and parts only of the circulatory system are represented, (a. m. m.) 



A, cuticle. B, epidermis, c, coelom. CM. layer of circular muscles. 

 D, seta. DV, dorsal vessel. E, cavity of intestine. F, typhlosole, filled 

 with ' hepatic ' cells. G , epithelium of intestine. H , ' hepatic ' cells. | , ventral 

 nerve-cord. J, nerve. K, ' giant fibres.' |_, nephrostome. |_M, layer of longi- 

 tudinal muscles. M, the point where the nephridium perforates the septum 

 between two segments : between the two cut ends the convoluted ' narrow 

 tube ' is intercalated, which is not shown in the figure. N, the first or long loop 

 of the nephridium. o, the second or short loop of the nephridium. P, the 

 third or terminal loop of the nephridium. R , external aperture of the nephridium . 

 SV, subneural vessel. V, intestinal vessel. VV, ventral vessel. 



